To evaluate the effect of a whole formula diet on nutritional and cognitive status in Alzheimer's disease patients. Patients were randomly assigned to two interventions: a whole formula diet based on lyophilised foods (Treatment Group, n=24) or nutritional advice (Control Group, n=29). Energy intake, body weight, biochemistry, Mini Nutritional Assessment (MNA) and Pfeiffer's tests were determined at baseline and at 3 months of treatment. No differences were observed between groups at baseline. Energy intake tended to increase in the Treatment Group and to decrease in the Control Group, although differences were not significant. The improvement in MNA and Pfeiffer test scores was not significantly different between groups. Body weight increased by 2.06+/-1.9 kg in the Treatment Group and by 0.32+/-3.04 kg in the Control Group (P=0.007). The increases in albumin (P=0.007), haemoglobin (P=0.002) and serum ferritin (P=0.009) were higher in the Treatment Group than in controls. A similar rate of serious adverse events (hospitalisation or death) was observed in both groups. Administration of this whole formula has a positive impact on nutritional status. The great diversity in textures and tastes enable these formulations to be administered to a wide range of patients with or without liquid dysphagia.